Tu Thanh Ha, The Globe and Mail
September 1, 2008
The controversial vaccine for cervical cancer that will be offered to schoolgirls in all Canadian provinces this fall triggers more severe allergic reactions than other vaccines, but the risk is still so tiny that HPV inoculation remains worthwhile, says a new Australian study.
The peer-reviewed paper, which was released Monday by the Canadian Medical Association Journal, was initiated after reports of severe allergic reaction, or anaphylaxis, in a school vaccination drive in New South Wales.
The study found that the estimated rate of anaphylaxis incidence was five to 20 times higher with the HPV vaccine than other vaccines. However, the research was done on a small number of incidents, limiting its statistical clout.
“All we’re doing is sounding a note of caution,” one of the authors, Peter McIntyre, head of Australia’s National Centre for Immunization Research, said in an interview from Sydney. “It’s still a rare occurrence [to have anaphylaxis].”
Also, earlier this year, the Medical Journal of Australia reported the case of a 26-year-old woman who suffered pancreatitis four days after her first dose of HPV vaccine. “A coincidental illness causing pancreatitis cannot be ruled out, but neither can HPV vaccination be excluded as a potential cause,” the authors wrote.
Despite the cautious tone of the Australian researchers, their findings may add fuel to the debate in Canada over HPV immunization.
With this fall’s return to school, HPV vaccine shots will be available to schoolgirls in all 10 provinces, following in the footsteps of Ontario and the Atlantic provinces, which began a year ago. But skepticism is high: In Ontario, for example, only half of eligible girls agreed to receive the vaccine last year.
The program is the most expensive vaccination campaign in Canadian history. A Merck Frosst product, the Gardasil vaccine protects against strains of human papillomavirus (HPV) responsible for 70 per cent of cervical cancers. Gardasil is costly, at $400 for the three required shots.
But some experts remain unconvinced, saying policy makers rushed into a pricey immunization program when there is no epidemic of cervical cancer, which can already be screened through regular Pap smears.
In a Canadian Medical Association Journal article last year, four researchers led by epidemiologist Abby Lippman of McGill University urged a more prudent course.
The New England Journal of Medicine echoed similar feelings in an editorial two weeks ago. “With so many essential questions still unanswered, there is good reason to be cautious about introducing large-scale vaccination programs,” it said.
The Australian study adds some reassurance, but there are still a lot of unanswered questions about the pertinence of HPV vaccine programs, Dr. Lippman said in an interview.
She noted that there was no clear data about the length of the immunity Gardasil confers and whether booster shots are needed. Also, she said, the program was approved amid intense marketing and political lobbying by Merck Frosst.
“The lobbying has been consistent and aggressive,” added Anne Rochon Ford, co-ordinator of the watchdog group Women and Health Protection, in a reference to Ken Boessenkool, a registered lobbyist for Merck Frosst in Ottawa who was a former senior policy adviser to Prime Minister Stephen Harper.
By June 30, 2008, more than half a million doses of HPV vaccine had been distributed in Canada.
There have been no confirmed cases of anaphylaxis in Canada, but 220 less severe “adverse” events have been reported, the Public Health Agency of Canada said.
Gardasil is “safe and effective,” the agency said in a statement, adding that the new study is inconclusive.
In the study, researchers confirmed seven cases out of 269,680 injections. This worked out to a rate of 2.6 incidents per 100,000 shots, compared for example with a 0.12 rate for a similar school inoculation for meningococcal C-conjugate in New South Wales.
However, because the sample size for the Gardasil study was small, its so-called confidence interval was broader, with a 95-per-cent possibility that the rate of anaphylaxis could be somewhere between 1.04 and 5.35. (Studies with large sample size result in a tighter interval).
The authors said the higher rate of reported incidents might stem not just from the vaccine’s components but also from the enhanced surveillance during school injections, and the fact that Gardasil was injected into young women, who, from mid-adolescence, have higher rates of anaphylaxis than men.
“Anaphylaxis following HPV vaccination is a rare event … and it should not curtail population-based HPV vaccination programs,” the study says.
In the same issue, the CMA journal also ran an editorial saying that the Australian study contributed to the public discourse about the vaccine while providing evidence that it was “remarkably safe.”
“There’s still many missing pieces of the jigsaw puzzle,” said Alan Cassels, a drug-policy researcher at the University of Victoria.
“This one is so new and the track record is so untested and the disease takes years to develop and is usually detectable with a Pap smear. There’s lots of reasons why you would hesitate.”
Source | See Also:Ãƒâ€šÃ‚Â Researchers Question Wide Use of HPV Vaccines | CDC reports almost 8,000 adverse reactions to “Gardasil” HPV vaccine in U.S. | Is HPV Vaccine to Blame for a Teen’s Paralysis? | Alberta to offer HPV vaccine this fall | Discovery of HPV in male oral cancers leads to vaccination call | HPV vaccination program raises concerns in B.C. | Gardasil shots have earned a painful reputation | Perspective on the HPV vaccine | Deaths associated with Merck’s HPV vaccine (Gardasil), over 3500 adverse affects reported | Political Intrigue in Merck’s Push for Mandatory HPV Vaccinations